Rotor Cooling Control for High-Speed Permanent Magnet Machines

The patent changes the temperature parameter of the permanent magnets by implementing a heating device that raises the magnet temperature from cold operating conditions (e.g., -20°C) to a controlled temperature range (e.g., 20-80°C). This parameter change reduces the pole wheel voltage significantly, allowing high rotational speeds to be operated without damaging the converter.

The patent applies preliminary action by heating the permanent magnets before high-speed operation begins. The heating device is activated in advance to raise the magnet temperature to an optimal range, thereby pre-conditioning the system to operate at high speeds without requiring restrictive field weakening control during operation. This maintains operational flexibility while ensuring converter protection.

Instead of changing the winding configuration, the patent changes the temperature parameter of the permanent magnets. By heating the magnets to an optimal temperature range, the magnetic flux strength is optimized, allowing the machine to maintain a good power factor with the existing winding design while still operating at high speeds without damaging the converter.

The patent inverts the conventional cooling approach by implementing a heating device instead. Rather than cooling the permanent magnets to improve efficiency, the system heats the magnets to reduce pole wheel voltage, thereby enabling high rotational speeds without converter damage. This inversion of the temperature control strategy resolves the contradiction between magnet temperature and speed capability.